摘要
城市污泥污染已经成为中国亟待解决的一个重大环境问题,采用厌氧发酵方法生产挥发性脂肪酸(VFAs)并进一步生产高附加值产品是实现污泥资源化利用的一条重要途径。在污泥中添加适量的厨余垃圾后厌氧发酵产挥发性脂肪酸可以明显提高VFAs的产量和底物的降解水平。为了考察污泥添加厨余垃圾发酵生产VFAs的特征以及预处理技术对发酵的影响,本研究在前期实验室研究的基础上,在25 L规模的厌氧发酵罐上对污泥添加厨余垃圾发酵产VFAs进行了研究,全文研究内容如下:
(1)厨余垃圾按总固体(TS)浓度为1:3的比例添加进污泥中进行厌氧发酵,考察了混合物不同TS浓度下厌氧发酵产VFAs的情况。结果显示添加厨余垃圾之后VFAs的累积量最高可达17.62g/L。综合产VFAs效果、底物降解效果和产率等情况,建议在较大规模的生产过程中选择130g/L的TS浓度为较合适的发酵产VFAs的底物浓度。对不同发酵底物浓度和产VFAs速率进行了初步的动力学研究,用Monod方程较好地拟合了产酸动力学过程,并得到动力学方程μ=(0.114·S)(281.764+S)(Ks:281.76g/L,μmax:0.114 g/h)。
(2)利用高压脉冲放电等离子体系(等离子体)和热-碱法对纯污泥和污泥添加厨余垃圾混合物进行预处理,研究了不同底物预处理过程中底物成分和性质的变化。等离子体预处理污泥时TS、VS、SCOD都有融出,但推测其中大部分是由于放电时系统温度升高从而对污泥进行热处理产生的。采用热-碱法对纯污泥和污泥厨余混合物进行预处理时TS、VS和SCOD的融出率略分别为42%、62%和72.5%。纯污泥和污泥厨余混合物的游离蛋白质的融出量分别达到64%和70.8%。游离碳水化合物的融出率均能达到50%以上。胞内物质的融出情况则是纯污泥经过热-碱预处理后胞内蛋白质融出较多,为0.019g/L;污泥厨余混合物预处理后则是胞内碳水化合物融出的较多,为0.014g/L。
(3)利用纯污泥和污泥添加厨余垃圾混合物预处理液进行发酵,研究了发酵产VFAs的情况。纯污泥和污泥添加厨余垃圾混合物经过热-碱预处理后发酵产VFAs比未经过热-碱预处理直接发酵得到的VFAs的量分别提高6.81g/L和3.30g/L,产率分别提高0.19g/gVS和0.23g/gVS。纯污泥发酵得到的是以乙酸为主要产物的VFAs,而污泥添加厨余垃圾混合物发酵后的VFA组成中乙酸和丁酸含量相当且都远大于其他单酸。在发酵过程中蛋白质比碳水化合物利用得多,游离蛋白质和游离碳水化合物是VFAs产生的主要底物来源,这其中又以游离蛋白质的贡献为主。
(4)纯污泥和污泥添加厨余垃圾混合物经过热-碱预处理后发酵的发酵液采用过滤和离心的方法进行固液分离,研究不同分离方法的分离效果。结果显示离心分离的效果优于滤布,过滤后固相含水率在80%以上,离心后固相含水率在80%以下;且污泥厨余混合物发酵液的分离效果比纯污泥发酵液的分离效果好。污泥与厨余垃圾混合经过预处理发酵后采用8000 r/min进行固液分离,从发酵液中得到的VFAs的得率最高为68.93%。
The pollution from sewage sludge has become a very serious and important environmental problem in China. Production of volatile fatty acids (VFAs) by anaerobic fermentation and further production of value added products by VFAs is one of potential strategies to realize the reuse and resource of the sewage sludge. Addition of kitchen wastes into the sewage sluge can enhance the VFAs production and substrate degradation efficiency during the anaerobic fermentation. In order to characterize the VFAs production from the mixed substrates, this study conducted the fermentation in a 25L fermentor on the basis of laboratory investigation by adding kitchen wastes into the sludge to produce VFAs The research processes and conclusions are as follows:
(1) Kitchen wastes were added into the sludge in the anaerobic fermentation with the ratio of kichen wastes and sewage sludge at 1:3. At this ratio the volatile fatty acids production under different concentrations was determined. The results showed that with the addition of the kitchen wastes, the accumulation of VFAs was up to 17.62 g/L. Based on an overall consideration of various factors, such as the VFAs production, substrate degradation and the production rates,130 g/L of TS concentration was considered the optimal fermentation substrate concentration to produce VFAs in a larger scale process. Additionally, the Monod equation was used to fit the dynamic process during anaerobic fermentation under different substrate concentrations and equation:μ=(0.114·S)/(281.764+S)(Ks:281.764 g/L,μmax:0.114 g/h) was obtained.
(2) Sewage sludge and the mixture (sludge and kitchen wastes) were pretreated by high-voltage pulsed discharge plasma systems (plasma) and thermo-alkaline respectively. The changes of substrate characteristics and composition were observed under different pretreatments. Pasma pretreatment changed the characteristics of sludge. However,it may be most attributed to the rising temperature in the system. The solubilization rate of TS, VS, SCOD are 42%,62% and 72.5%, respectively, when the mixture (sludge and kitchen wastes) substrates are pretreated by thermo-alkaline. The solubilization of dissociative protein is 64% and 70.8% respectively when the sludge and mixture (sludge and kitchen wastes) after pretreatments. Meanwhile the solubilization of dissociative carbohydrate could exceed 50%. The solubilization of intracellular material revealed that the sludge through the thermo-alkaline pretreatment released more intracellular proteins (0.019g/L), while the mixture (sludge and kitchen wastes) after hot alkaline pretreatment released more intracellular carbohydrate (0.014 g/L).
(3) The production of VFAs during fermentation after different pretreatments with pure sludge or mixed sludge was studied, respectively. After the heat-alkaline pretreatment, the VFAs from the sludge and the mixture (sludge and kitchen wastes) have increased by 6.81 g/L and 3.30 g/L, the production rates have increased by 0.19 g/gVS and 0.23 g/gVS. The main products in VFAs was acetic acid during the sludge fermenting, but we got acetic acid and butyric acid in the VFAs more than other single acids when fermented the mixture (sludge and kitchen wastes). In the process of fermentation, protein were more exploited than carbohydrates, both of them with the dissociative form were the major source of product VFAs, but the free protein was the main contribution source. (4) The method of filtration and centrifugation were used to separate the fermentation liquid after thermo-alkaline pretreatment. The effects of separation about different methods process (pretreatment, fermentation and sepration) were evaluated. The results revealed that the effect of centrifugation was better than filtration; the moisture content within solid was above 80% after filtration while the moisture conten was below 80% after centrifugation.The effect of separation about the mixture (sludge and kitchen wastes) was better than the sludge. We got the highest yield of VFAs as 68.93% when the fermentation broth of the mixture (sludge and kitchen wastes) after centrifugation.
引文
[1]曹秀芹,陈珺.污水处理厂污泥处理存在问题分析[J].北京建筑工程学院学报,2002,18(1):1-4
[2]Wang W, Luo Y X, Qiao W. Possible solutions for sludge dewatering in China [J]. Frontiers of Environmental Science & Engineering in China,2010,4 (1):102-107
[3]铁道部专业设计院标准处等.污水处理的基本方法及应用[M].中国铁道出版社,1982
[4]金儒霖,刘永龄.污泥处置[M].北京:中国建筑出版社,1982
[5]Chen H, Wu H Y. Optimization of volatile fatty acid production with co-substrate of kitchen wastes and dewatered excess sludge using response surface methodology[J]. Bioresource Technology,2010,24 (2):27-30
[6]余杰,田宁宁,王凯军,等.中国城市污水处理厂污泥处理处置问题探讨分析[J].环境工程学报,2007,1(1):82-86
[7]王晓吡,詹健,康晓荣,等.中国城市污水厂污泥处理处置技术[J].江西化工,2007,3:24-27
[8]Hudson J A. Sewage sludge incineration:some planning and operating experiences[C]. In IWEM Year BOOK,1992
[9]钱泽澍,闵航.沼气发酵微生物学[M].杭州:浙江科学技术出版社,1985
[10]Cadoret A, Conrad A, Block J-C. Availability of low and high molecular weight substrates to extra cellular enzymes in whole and dispersed activated sludges[J]. Enzyme and Microbial Technology,2002,31 (1-2):179-186
[11]任南琪,王爱杰.厌氧生物技术原理与应用(第一版)[M].北京:化学工业出版社,2004
[12]王琴.污泥停留时间及温度对剩余污泥连续生产短链脂肪酸的影响[D]:[硕士学位论文].上海:同济大学环境科学与工程学院,1998
[13]贺延龄.废水的生物处理[M].北京:中国轻工业出版社,1998
[14]李艳霞,陈同斌,罗维,等.中国城市污泥有机质及养分含量与土地利用[J].生态学报,2003,11:2464-2474
[15]Tiehm A, Nickel K, Neis U. The use of ultrasound to accelerate the anaerobic digestion of sewage sludge [J]. IAWQ,1997,36(11):121-128
[16]Sambhunath G, John R C, Donald L K. Anaerobic acidogesis of wastewater sludge [J]. WPCF.1975,47(1):30-45
[17]刘晓玲.城市污泥厌氧发酵产酸条件优化及其机理研究[D]:[博士论文].江苏:江南大学,2009
[18]Iranpour R, Stenstrom M, Tchobanoglous G. Environmental engineering energy value of replacing waste disposal with resource recovery [J]. Science,1999,285 (5428):706-711
[19]Largus T A, Khursheed K, Muthanna H A, et al. Production of bioenergy and biochemicals from industrial and agricultural wastewater [J]. Trends in Biotechnology, 2004,22 (9):477-485
[20]Kim S H, Han S K, Shin H S. Feasibility of biohydrogen production by anaerobic co-digestion of food waste and sewage sludge[J]. International Journal of Hydrogen Energy,2004,29:1607-1616
[21]杨亚静.污水处理厂污泥酸性发酵实现挥发酸产量最大化实验研究[D]:[硕士学位论文].山西:太原理工大学,2006
[22]叶小梅,常志州.有机固体废物干法厌氧发酵技术研究综述[J].生态与农村环境学报,2008,24(2):76-79
[23]Angel I D, Sanders W. Assessment of the Anaerobic Biodegradability of MacroPollutants[J]. Reviews in Environmental Science and Biotechnology,2004,3 (2): 117-129
[24]Song H. Characterization of microbial community structure within Anaerobic Biofilms on municipal solid waste[D]. Queensland:School of Engineering, the University of Queensland,2003.
[25]Banerjee A, Elefsiniotis P, Tuhtar D. Effect of HRT and temperature on the acidogenesis of municipal promary sludge and industrial wastewater [J]. Water Science and Technology,1998.
[26]张希衡.废水厌氧生物处理工程[M].北京:中国环境科学出版社.1996
[27]Stroot P G, McMahon K D, Mackie, R I, et al. Anaerobic codigestion of municipal solid waste and biosolids under various mixing conditions—Ⅰ. digester performance [J]. Water Research,2001,35 (7):1804-1816
[28]任南琪,王爱杰,马放.产酸发酵微生物生理生态学[M].北京:科学出版社,2005.51-135
[29]Agdag O N, Sponza D T. Co-digestion of industrial sludge with municipal solid wastes in anaerobic simulated landfilling reactors[J]. Journal of Hazardous Materials,2007(140): 75-85
[30]付胜涛,于水利,严晓菊,等.剩余活性污泥和厨余垃圾的混合中温厌氧消化[J].环境科学,2006,27(7):1459-1463
[31]Min K S, Khan A R, Kwon M K, et al. Acidogenic fermentation of blended food-waste in combination with primary sludge for the production of volatile fatty acids[J]. Journal of Chemical Technology and Biotechnology,2005,80:909-915
[32]Lee M, Hidaka T, Hagiwara W, et al. Comparative performance and microbial diversity of hyperthermophilic and thermophilic co-digestion of kitchen garbage and excess sludge[J]. Bioresource Technology,2009,100:578-585
[33]Valo A, Carrere H, Philippe D J. Thermal chemical and thermo-chemical pre-treatment of waste activated sludge for anaerobic digestion[J]. Journal of Chemical Technology and Biotechnology,2004,79:1197-1203.
[34]Vlyssides A G, Karlis P K. Thermal-alkaline solubilization of waste activated sludge as a pre-treatment stage for anaerobic digestion[J]. Bioresource Technology,2004,91: 201-206.
[35]何玉凤.热-碱处理促进剩余污泥水解的试验研究[D]:[硕士学位论文].大连:大连理工大学,2007
[36]肖本益,刘俊新.污水处理系统剩余污泥碱处理融胞效果研究[J].环境科学,2006,27(2):319-323
[37]何玉凤,杨凤林,胡绍伟,等.碱处理促进剩余污泥高温水解的试验研究[J].环境科学,2008,29(8):2260-2265
[38]Vlyssides A G, KarJis P K, Thermo-alkaline solubilization of waste activated sludge as a pre-treatment stage for anerobic digestion[J]. Water Science and Technology,2004,91: 201-206
[39]秦曾衍,左公宁,王永荣,等.高压脉冲放电及其应用[M].北京:北京工业出版社,2000
[40]张灿.液中放电等离子体技术降解TNT废水的装置和试验研究[D]:[博士学位论文].重庆:重庆大学城市建设与环境工程学院,2006
[41]Sugiarto A T, Sato M. Pulsed plasma processing of organic compounds in aqueous solution [J]. Thin Solid Films,2001,386:295-299
[42]戚以政,汪叔雄.生化反应动力学与反应器[M].北京:化学工业出版社,1999
[43]伍珂,刘和,堵国成,等.产气抑制剂对污泥和食品废弃物混合发酵产酸过程的应用研究[J].工业微生物.2009.39(1):32-36
[44]Wooshin P, Seung H H, Oh S E, et al.Removal of headspace CO2 increases biological hydrogen production [J]. Environmental Science and Technology.2005,39:4416-20
[45]张宇.发酵动力学研究、开发与应用新进展[J].中国新技术新产品,2009,21:7
[46]国家环保局《水和废水监测分析方法》编委会[M].北京:中国环境科学出版社,2002
[47]潘平,康清蓉,李晓.分光光度法测定土壤中总磷[J].光谱实验室,2003,20(5):697-699
[48]郑元景,沈永明,沈光范.污水厌氧生物处理[M].北京:中国建筑工业出版社,1988
[49]Lei Y F, Chen Y G, Zheng X. Enhancement of Waste Activated Sludge Protein Conversion and Volatile Fatty Acids Accumulation during Waste Activated Sludge Anaerobic Fermentation by Carbohydrate Substrate Addition:The Effect of pH [J]. Environmental Science and Technology,2009,43:4373-4380
[50]吕凡,何品晶,邵立明,等.pH值对易腐有机垃圾厌氧发酵产物分布的影响[J].环境科学,2006,27(5):991-997
[51]Parawira W, Murto M, Read J S, et al. Volatile fatty acid production during anaerobic mesophilic digestion of solid potato waste [J]. Chemical Technology and Biotechnology,2004,79(7):673-677
[52]刘和,聂艳秋,许科伟,等.产乙酸耦合系统产酸及其微生物种群动态分析[J].中国环境科学.2008.28(4):319-323
[53]Elango D, Pulikesi M, Baskaralingam P, et al. Production of biogas from municipal solid waste with domestic sewage [J]. Journal of Hazardous Materials.2007,41, 301-304.
[54]Borowski S, Szopa J S. Experiences with the dual digestion of municipal sewage sludge [J]. Bioresource Technology,2007,98:1199-1207
[55]毕东苏,郑广宏,陆烽.剩余污泥厌氧发酵过程中氮的转化规律与计量关系[J].生态环境.2008.17(4):1403-1406
[56]赵志宏,廖德祥,李小明,等.厌氧氨氧化微生物颗粒化及其脱氮性能的研究[J].环境科学,2007,28(4):800-805
[57]徐伟锋,陈银广,张芳,等.污泥龄对A/A/O工艺反硝化除磷的影响[J].环境科学,2007,28(8):1693-1696
[58]郭磊,刘和,堵国成,等.底物浓度对多级逆流工艺厌氧发酵城市污泥产酸的影响[J].食品与生物技术学报,2009,28(4):544-549
[59]刘振玲,堵国成,刘和,等.食品废弃物厌氧消化产乙酸的研究[J].环境污染与防治,2007,29(1):49-52
[60]谢波,郭亮,李小明,等.三种预处理方法对污泥的破解效果[J].中国环境科学,2008,28(5):417-421
[61]史富丽,杨世东,马军,等.催化高压脉冲放电降解水中苯酚[J].工业水处理,2005,25(11):40-43
[62]Bradford M M. A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of pro-tein-dyebinding [J]. Analytical Biochemistry, 1976,72:248-254.
[63]Dubois M, Gilles K A, Hamilton J K, et al. Colorimetric method for determination of sugars and related substances [J]. Analytical Chemistry,1956,28:350-356
[64]王治军,王伟.热水解预处理改善污泥的厌氧消化性能[J].环境科学,2005,26(1):68-71
[65]胡亚冰,张超杰,张辰,等.碱解处理对剩余污泥融胞效果及厌氧消化产气效果[J].四川环境.2009,28(1):2-4
[66]肖本益,刘俊新.不同预处理方法对剩余污泥性质的影响研究[J].环境科学,2008,29(2):327-331
[67]孙弘,李清彪,王远鹏,等.预处理法促进剩余活性污泥生产VFAs[J].化学工程与装备,2009,7:165-168
[68]Lin J G, Chang C N, Chang S C.Enhancement of anaerobic digestion of waste acdvated sludge by alkalille solubinization[J]. Bioresource Technology,1997,62:85-90
[69]Lata K, Rajeshwari K V, Pant D C, et al. Volatile fatty acid production during anaerobic mesophilic digestion of tea and vegetable market wastes[J]. World Journal of Microbiology and Bio-technology,2002,18 (6):589-592
[70]发酵液的预处理和固液分离方法[DB/OL].http://rywen.net/view/175801,2008.
[71]顾觉奋主编.分离纯化工艺原理[M].北京:中国医药科技出版社,2002
[72]Lahdheb H, Bouallagui H, Hamdi M. Improvement of activated sludge stabilisation and filterability during anaerobic digestion by fruit and vegetable waste addition[J]. Bioresource Technology,2009,100:1555-1560